<nz-button-group>
  <button nz-button nzType="primary" [disabled]="!canUndo" (click)="undo()"><i nz-icon nzType="undo"
      nzTheme="outline" nz-tooltip nzTooltipTitle="撤销"></i></button>
  <button nz-button nzType="primary" [disabled]="!canRedo" (click)="redo()"><i nz-icon nzType="redo"
      nzTheme="outline" nz-tooltip nzTooltipTitle="恢复"></i></button>
  <button nz-button nzType="primary" (click)="center()"><i nz-icon nzType="align-center"
      nzTheme="outline" nz-tooltip nzTooltipTitle="居中"></i></button>
  <button nz-button nzType="primary" (click)="centerContent()"><i nz-icon nzType="align-center"
      nzTheme="outline" nz-tooltip nzTooltipTitle="内容居中"></i></button>
  <button nz-button nzType="primary" (click)="minMap()"><i nz-icon nzType="pic-left"
      nzTheme="outline" nz-tooltip nzTooltipTitle="略缩图"></i></button>
  <button nz-button nzType="primary" (click)="export()"><i nz-icon nzType="export" nzTheme="outline"
      nz-tooltip nzTooltipTitle="导出svg"></i></button>
  <button nz-button nzType="primary" (click)="export('png')"><i nz-icon nzType="export"
      nzTheme="outline" nz-tooltip nzTooltipTitle="导出图片"></i></button>
  <button nz-button nzType="primary" (click)="clear()"><i nz-icon nzType="clear" nzTheme="outline"
      nz-tooltip nzTooltipTitle="清空"></i></button>

</nz-button-group>

<button nz-button (click)="exportJson()">export json</button>
<button nz-button (click)="importJson()">import json</button>
